In a liquid crystal display device (a display device) equipped with a non-light-emitting liquid crystal display panel (a display panel), the liquid crystal display panel is usually also equipped with a backlight unit (an illumination device) for supplying light. The backlight unit is preferably configured so as to generate planar light that pervades throughout the entire planar liquid crystal display panel. Therefore, the backlight unit installed in the liquid crystal display device sometimes includes a light-guiding plate (a light-guiding member) for mixing together light from an internal light source to a high degree.
A known example of a backlight unit containing a light-guiding plate is an edge light (side light) type backlight unit. An edge light type backlight unit is commonly configured with a light source such as an LED (light emitting diode) disposed on the side surface of a light-guiding plate. In a backlight unit having this type of configuration, light emitted from the light source is incident on the light-guiding plate interior from the side surface of the light-guiding plate, and the incident light is guided by the light-guiding plate interior and emitted toward the liquid crystal display panel.
An example of such a backlight unit is disclosed in Patent Literature 1, for example.
Patent Literature 1 discloses an illumination device in which a trapezoidal shape protrudes in a position corresponding to a point light source in the light-guiding plate, and a symmetrical triangular or trapezoidal through-hole (perforation) is provided within this trapezoidal shape. In this illumination device, light from the light source is reflected by the side surface of the protruding trapezoidal shape or the side surface of the through-hole (the perforation), whereby the light incident on the light-guiding plate spreads to the left and right. Uniform outgoing light is thereby achieved.